Can one heat a stud wall and use it instead of a radiator?
If instead of a rad of 8 sqft we warm an 80 sqft internal stud wall, the wall surface temp rise only need be around 1/10th that of the rad. So instead of 50C above 20 it would need to be around 5C above 20, or
25C. This is a non-problematic wall surface temperature.Presumably the heating would be carried out by microbore with ali fins inside the wall.
Is it workable?
NT
You be using air to move the heat from the pipe to the wall which I don't think is all that efficient but what else you'd use I'm not sure.
This is a really interesting idea.
Its basically UFH done vertically!
I won't be as nice as UFH, but it certainly will work.
You will need to pack the wall with insulation, to avoid heating the room the other side, and run water pipes inside it..use standard UFH pipe..
..also use a temperature reducing system..80C water in a wall isn't going to do the studs a lot of goos!
It works fine..the key is to make sure the air is a lower thermal resistance path than the wall to the next room (or to outside)by using plenty of celotex behind the pipes.
It should work, in principle. I'm not sure that you can simply scale surface areas and delta-Ts linearly though because the convection and radiation characteristics will both be different from those of a conventional radiator. As long as you can fine tune the actual wall temperature, it's probably ok.
I think the tubes will need to be on metal plates bonded to the back of the plasterboard rather than relying on convection inside the cavity, and - as others have said - you'll have to insulate to stop the heat going the wrong way.
You'll also have to be very careful when subsequently drilling into the wall!
================================ Skirting radiators ('Finrad') used 22mm pipes with 3" square aluminium foil fins spaced about 1" apart. You might be able to find some of these but in any case I think 22mm would be far better than 8 /10mm microbore even without fins. You would probably need to make up a manifold rather than have a continuous length of pipe.
Given the area you're considering you'll probably get quite a good result compared with skirting heaters since you'll be able to pack so much more into your wall.
Cic.
This is what lies behind underfloor heating, large area, low temperature (and thus ideally suited to condensing boilers or heat pumps). Underfloor heating, though, puts the heat into the room at the most desirable place, low down.
The other problem with your idea is that you're presumably putting a sheet of plasterboard in front of the heat source which will seriously impact the heat flow.
Yes.
It's not a simple linear relationship, the proportions of heat emitted by radiation/convection are very different.
Pex with ali spreader plates, as per UFH.
Been done, a lot.
I've wondered about using a stud wall. It should be no different to UFH, spreader plates could be used, or sand/ dry mix used as a heat transfer/storage medium. Has anyone tried it?
Plasterboard - thermal resistance of 0.16W/mK. For 12mm, that's around
20 W/m^2/K, or 200W/K.For 3Kw, 15C or so.
Cement board - aquapanel - will drop this to around 2C.
If it was me, I would try to make this as following.
Take a lot of 3*2, and saw in 15mm or so deep 15mm wide cuts with a circular saw.
Put up this 3*2 as a framework, on 60cm or so centres.
Put the pipes horizontally, zig-zagging down at the edges, with the heat going in at the top.
Now, place 2*2 or so against the 3*2s, and screw down.
Place kingspan into the back, and seal with tape on the front side, so no leaks can happen. Place temporary sheets of 18mm WBP on either side, screwed securely.
Pour in a nice strong mix of concrete, and allow to set for a day or so.
On the side of each bay, place 10mm or so of polystyrene or something, to allow for horizontal expansion.
Remove the WBP, and plasterboard the 'cold' side, and then the hot side.
This would be ideally suited for tile, though this may not be appropriate.
Yes. We were considering building a house in Germany, and went to see a German green builder (=D6kohaus Ibach). Their office / show-home had this set-up, but they said it was a bit of a failed experiment. Two major problems: a) cracking in the plaster; b) picture hooks / shelves / etc were a bit of a no-no!
================================ Neither problem would be insurmountable though. There are plenty of alternatives to plaster / plasterboard and many different ways of having pictures and shelves.
Cic.
I dont understand why you all want to insulate this wall. Since its an internal wall, with no insulation it will heat 2 rooms, ie do twice the work at half the price.
I realise the relationship isnt really linear, the initial calc just gave a rough figure to begin with, which seemed to indicate it being a runnner. Since the the required rise is so small I think we could safely leave it to regulate its own temp with a TRV or roomstat, just as a metal radiator does.
Yes, thats my prime reservation. The wood would be cycled from room temp in summer, and overnight in winter, to 80C or whatever during winter days.
Would use of knot free wood be ok, or would it be ok if pipes were attached symmetrically to each upright? I feel doubtful about that.
OTOH suspending the vertical pipe runs would mean the wood studs will only see a fraction of this temp rise.
Lastly, perhaps enginered wood could be used if needed, or maybe steel studwork.
Well, you can drill into the studs all you want, except at the very top and bottom where a horizontal run will be needed. Seems like a good price to pay to have no rads or one less rad, which itself represents a large no-drill area.
If the vertical runs are unattached, firstly drilling the shallow PB isnt overly likely to hit them, and 2nd if it does they'll just push out the way. It would take very persistent drilling to get through completely unsupported microbore, and the drill goes through plasterboard so quick and easy I dont see that happening.
So to my surprise, it looks mostly drillproof.
Rigid pipe would be a lot more work to install though. I was hoping to make it an easier quicker job. If full water temp is used, not a reduced temp circuit as with ufh, parallel microbore should be sufficient.
Perhaps we could plumb it in 2 parallel circuits, one covering the top half and one the bottom half. The top circuit could then be turned down or even off if desired.
Or have the bottom circuit do the work until it gets really cold and needs the contribution of the top circuit as well. Not sure how to arrange that ubersimply though, 2 room stats or an outdoor stat plus electric valves would be additional expense and work.
While we have low conductivity, we also have large surface area and very low output per square requirement. I dont see that as a problem.
With 70C HW the PB will drop the majority of 70-25=45C. So it will be able to conduct anything upto 45x20 W/m^2 = 900w/sqm, and we only need a wee fraction of that. So it looks like PB is an order of magnitude more conductive than our minimum requirememnt for this.
Presumably that might be controlled in any of the following ways:
Picture hooks are just hollow wall anchors, I dont see those being a problem. Shelves screw into the uprights, so ditto.
I cant help but wonder whether these 2 issues might be as much down to their particular design as the concept itself.
This looks good. Thanks to everyone for developing this one. Anyone know more about the expansion/cracking side of things?
NT
Indeed. I'd probably use MDF.
Cracking IS a problem, but lining paper would sort that.
Oh, fine, yif thats what is needed.
Yep.
That is too much. You want to keep water temps down to around 45C max, and use a LOT of pipe.
Yup. Thats the way..come in at the wall center, and loop up and down between the studs and then loop all the way back.
Steel would be good.
Yup
Don't necessarily use microbore: I;d use normal 15mm plastic UFH pipe. You could use normal pipe clamps to hold it to the studs.
Use plastic pipe. That's whats under my floor..
Could do.
Another possiblity is to run hot in at the base and out at the top after its cooled down.
Yep. My floor has 3" of concrete, then a foamie layer, then engineering wood.
Still gets loads hotter under the sofa than in the middle of the floor..that floor really does conduct through.
My only worry is going much over 50C on the internal structure.
A thicker skim with scrim tape will sort that.
Its the joins, not the PB, you need to worry about.
Expansion isn't great with heat..its the likelihood of huge summer to winter humidity variations that bothers me. I hve a wall fill of pipes and it has shrunk hugely since construction, and it moves summer to winter..but it seems to be stabilising.
Some. I think the key thing is to work out the real temperature you need and then keep the water as low as temp as you can get away with.
Up to 50C I do not see a problem..over that I would be concerned.
Have a look at
A nice idea but you cant use a normal radiator as the basis for even rough calculations
Normal radiators are really convectors - just look at the increase in outputs when you start adding a second panel and convector fins.
A large heated wall is likely to have very different heat transfer properties - underfloor heating is probably a far better model to use for rough calculations. Robert
You lose the option to control the individual rooms.
Expect at best 100W/sq meter.
Possibly as low as 50W
=============================== Since the OP is contemplating a rather unusual form of heating I think he should consider making this *radwall* into something of a designer feature in his home. This opens up all kinds of possibilities such as aluminium frame / translucent glass / aluminium or copper sheet / louvred wood / metal etc. The possibilities are almost limitless. Once you've called something 'designer' you can get away with almost anything.
Cic.
True. Cover teh wall with aluminium cladding as used to make containers for shipping..that would increase the surface area and provide a conductive path..;-)
Or better still, go to a computer recycling place and dot and dab the wall with a plating of computer CPU heatsinks, sprayed a nice set of colors - could do a mosaic type design.
The mind boggles
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.